Both my bikes have flat (mountain bike-style) bars. I've tried a few mirrors but the one that really works is a CRG motorcycle mirror. I had one sitting in my parts bin, and one day I realized that bike bars and moto bars are the same diameter at the ends. I tried it, and it works better than any bicycle mirror -- no vibration, great field of view, stays where I put it but folds in when I take the bike on the train, and is nearly indestructible. Granted, it weighs a little more than a typical bicycle mirror, but it's beautifully machined solid aluminum instead of flimsy plastic.